Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON):

Solution:
from Queue import Queue
d = [0, 1, 0, -1]
h, w = map(int, raw_input().split())
m = list()
m.append(["#" for _ in xrange(w+2)])
for _ in xrange(h):
    m.append(["#"]+list(raw_input())+["#"])
m.append(["#" for _ in xrange(w+2)])
dat = len(filter(lambda x:x==".", [i for j in m for i in j]))

q = Queue()
q.put((1,1,1))

while not q.empty():
    xy = q.get()
    if not m[xy[0]][xy[1]] == ".":
        continue
    m[xy[0]][xy[1]] = xy[2]
    for i in xrange(4):
        e = (xy[0]+d[i], xy[1]+d[i+1&3], xy[2]+1)
        if m[xy[0]+d[i]][xy[1]+d[i+1&3]] == ".":
            q.put(e)

try:
    print dat-m[h][w]
except:
    print -1